Flight, January 1923

THE PARIS AERO SHOW 1922

S.I.A. LATECOERE, Toulouse

   ONLY one machine was exhibited this year by Societe Industrielle d'Aviation Latecoere, but what the exhibit lacked in numbers it made up for in size. The Latecoere "L.A.T.6" is a huge four-engined bomber, with the 260 h.p. Salmson engines placed in tandem on the wings. The fuselage of this machine was exhibited at the 1921 Paris Show, when both its design and construction came in for considerable criticism. Nor is it probable that the critics, after seeing the finished machine, will have changed their views. To begin with, the tandem arrangement of engines has been found years ago to be bad aerodynamically, owing mainly to the fact that the airscrew of the rear engine is working in the slip stream from the tractor, and consequently has to have a greater pitch, as it is working in air of greater velocity. Secondly, the many projections on the machine must have a very adverse effect upon the efficiency, although if the advantages aimed at are attained, this price might not be considered unduly great. In the "L.A.T.6" the reasons have obviously been to provide gun platforms in positions where there was a good field of fire, so as to enable the machine to be independent of escorts for fighting off attackers. Thus there is a gunner's cockpit in the extreme nose, and another aft of the wings, formed by a projection shaped somewhat like the counter of a yacht, from which the gunner can sweep an entire semi-circle, or even slightly more.
   Constructionally the Latecoere bomber is of interest mainly on account of the fact that it is built of Duralumin. In spite of its great size the L.A.T.6 has but one pair of inter-plane struts on each side, and this in spite of the fact that the engines are mounted on the wings. The wings are built up of a number of spars, of which the two main ones are double. These are of the lattice type, as are also the single auxiliary spars or stringers. The ribs are little more than fiat bands passed over the main and secondary spars, being in fact of very flat trough section and serving mainly for the attachment of the sheet Duralumin covering.
   The wing bracing is of interest on account of the fact that the lift wires pass through the lower plane from the undercarriage struts, and are attached at the top, not to the spars, as is usual practice, but to the large-diameter compression tube of the drag bracing. This tube passes through the centre of the spars, and by attaching to them the lift and anti-lift wires and inter-plane struts the fitting is considerably simplified. We have seen the same arrangement before, on, we believe, the Boulton and Paul all-metal two-seater shown at one of the Paris Aero Shows.
   The undercarriage has been entirely re-designed since the previous Show, when the fuselage of the L.A.T.6 was shown with two short wing roots and the undercarriage struts passing through the lower plane, inside which the shock absorbers were housed. At the recent Paris Show the machine was exhibited with a very wide undercarriage, consisting of a set of wheels under each pair of engines. Triangulation was by means of the wing bracing, no transverse bracing being employed between the two halves of the undercarriage.
   The main characteristics of the L.A.T.6 are as follows :- Length, o.a., 51 ft. 8 in.; span, 84 ft.; height, 20 ft. 6 ins.; wing area, 1,300 sq. ft.; total loaded weight, 11,600 lbs.; wing loading, 9 lbs. /sq ft.; power loading (1,000 h.p.), 11.6 lbs./h.p.; estimated speed near ground, 142 m.p.h.; speed at 13,000 ft. 133 m.p.h.